Optical phased array antenna using optical waveguide with hybrid lattice structure and lidar including the same

Abstract

To provide an optical phase array antenna based on an optical waveguide type with a hybrid grating structure and LIDAR including the same.SOLUTION: An optical phase array antenna includes: a coupling unit for receiving light from a light source; a light distribution unit for distributing light propagated from the coupling unit to a plurality of optical paths; a phase modulation unit for modulating a phase of the light distributed from the light distribution unit; and a light output unit that outputs the light modulated by the phase modulation unit, and includes an antenna element waveguide extending at a predetermined length through which the light propagates, and a clad layer formed to surround the antenna element waveguide. The antenna element waveguide has a first recessed portion recessed downward with respect to an upper surface thereof. The clad layer has a second recessed portion recessed downward with respect to an upper surface thereof at a position adjacent to the first recessed portion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical phased array antenna of an optical waveguide type having a hybrid lattice structure, and a LiDAR (Light Detection And Ranging) device including the same. [Background technology]

[0002] Lidar sensors for autonomous vehicles obtain 3D spatial information by measuring the time it takes for an incident pulsed laser to be reflected by an object and return. They can be broadly divided into 'flash type' and 'scanning type' depending on the laser emission method. The flash type is a method of simultaneously scanning a wide area with a laser beam, and the light receiving element is in a 2D-array form so that the receiver can also recognize the reflected image. In contrast, scanning type Lidar performs point mapping in 3D space through the vertical and horizontal rotation of the laser beam. To achieve this, it has a lower laser light source output and a simpler receiver light receiving element structure compared to the flash type. Existing scanning type Lidar has a 360° viewing angle due to the rotation of a mechanical motor.

[0003] However, basic mechanical lidars require heavy motors for rotation and consume a lot of power, making them unusable in unmanned aerial vehicles that require limited power and weight. Furthermore, the mechanical rotation speed cannot match the rotation speed required for autonomous vehicles traveling on highways.

[0004] An optical phased array antenna distributes an incident laser to each antenna element through several directional couplers, and modulates the phase of the distributed laser to obtain the desired output laser propagation direction.

[0005] To increase the maximum measurement distance of a lidar, the antenna requires higher laser output, but silicon waveguides, which have low laser threshold power and high linear and nonlinear losses, are at a disadvantage compared to silicon nitride waveguides.

[0006] Silicon nitride waveguides have a low refractive index, which increases the magnitude of the evanescent wave of the waveguide mode, and therefore can easily interact with adjacent waveguides that have the same propagation constant. In order to expand the limited horizontal viewing angle of optical phased array antennas, the spacing between antenna elements must be close to a distance of about half the wavelength, but the closer the spacing between antenna elements is, the more crosstalk between adjacent elements will cause, making it difficult to obtain the desired output phase distribution.

[0007] In the case of lidar intended to be installed inside autonomous vehicles, normal operation without being affected by temperature changes inside the vehicle (-40 to 85°C) is important for the safety of passengers and pedestrians, so the phase change caused by local heating that can be used with silicon nitride waveguides is difficult to use.

[0008] In planar optical elements fabricated on a wafer, the signals transmitted through the waveguide are emitted at similar rates to the top and bottom of the chip due to vertical refractive index symmetry, making it difficult for them to have clear spatial directionality. Also, the signal emitted to the bottom of the chip is reflected upward from the boundary surface at the bottom, causing interference with the signal emitted to the top, generating unwanted noise.

[0009] As a related art of optical phased array antennas, the applicant has disclosed Korean Patent No. 10-1924890 entitled "Optical phased array antenna and lidar including same". The related art discloses a structure in which the height of the antenna element waveguide of the optical output section is changed and a plurality of diffraction gratings with higher antenna element waveguide heights are provided at intervals. This structure has the advantage that the incident laser can be output in the desired direction without using a mechanical driving device and the influence of changes in the external environment is minimized.

[0010] However, recently, there is an increasing need for an optical phased array antenna with improved directivity. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent Publication No. 10-1924890: Optical phased array antenna and lidar including the same. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been devised to solve the above-mentioned problems.

[0013] First, the present invention proposes an optical phased array antenna structure for developing a LIDAR for autonomous driving and unmanned aerial vehicles based on an optical phased array antenna, which replaces the existing mechanical rotation method and aims to develop a LIDAR that is lighter, cheaper, and easier to mass-produce than existing ones.

[0014] Secondly, the present invention aims to propose an optical phased array antenna structure with improved directivity and reduced perturbation strength compared to the prior art.

[0015] Third, the present invention proposes an optical phased array antenna structure that can be manufactured using CMOS semiconductor process technology, has a maximum output of 2W or more, a horizontal viewing angle of 120° or more, and a vertical viewing angle of 20° or more, and that provides an increase in the signal-to-noise ratio through structural modification of the optical phased array antenna. [Means for solving the problem]

[0016] In one embodiment of the present invention to solve the above problems, an optical phased array antenna includes a coupling unit that receives light input from a light source, an optical distribution unit that distributes the light propagated from the coupling unit into a plurality of optical paths, a phase modulation unit that modulates the phase of the light distributed by the optical distribution unit, and an optical output unit that outputs light modulated by the phase modulation unit, the optical output unit including an antenna element waveguide through which the light is propagated and extended by a predetermined length, and a cladding layer formed to encase the antenna element waveguide, the antenna element waveguide having a first recessed portion that is recessed downwardly with respect to an upper surface, and the cladding layer having a second recessed portion that is recessed downwardly with respect to an upper surface at a position adjacent to the first recessed portion.

[0017] The cladding layer has a second lead-in portion formed at a position spaced apart from the first lead-in portion along the length of the antenna element waveguide so that the second lead-in portion faces a portion of the remaining area of ​​the antenna element waveguide excluding the first lead-in portion.

[0018] The first lead-in portion is formed to have a predetermined width from one end to the other end based on the length direction of the antenna element waveguide, and the second lead-in portion is formed to have a predetermined width from one end to the other end based on the length direction of the antenna element waveguide, but is formed so that the other end is spaced apart from the other end of the first lead-in portion by a predetermined offset distance along the length direction of the corresponding antenna element waveguide.

[0019] The offset distance is preferably close to 0.3 μm.

[0020] The second lead-in portion may be formed to have a width corresponding to a width of the first lead-in portion in a length direction of the antenna element waveguide.

[0021] The second recessed portion is preferably recessed downward into the upper surface of the cladding layer by a predetermined depth such that a bottom surface of the second recessed portion is adjacent to the upper surface of the antenna element waveguide.

[0022] The first lead-in portions may be formed in a plurality (at least 3, 5, 10, or 20) spaced apart from one another along the length of the antenna element waveguide.

[0023] It is preferable that a plurality of the second recessed portions are formed in the cladding layer so as to be spaced apart from each other along the length of the antenna element waveguide.

[0024] The first recessed portions are spaced apart from each other by a length corresponding to a width of the antenna element waveguide in the longitudinal direction.

[0025] The optical output section is configured by stacking a lower layer and an upper layer vertically on top of a base layer, and the first recessed portion is formed by etching an upper portion of the lower layer, and the second recessed portion is formed by etching an upper portion of the upper layer.

[0026] Meanwhile, a method for processing an optical output portion of an optical phased array antenna according to the present invention includes: (a) preparing a silicon-on-insulator (SOI) having first to third layers stacked thereon (S110); (b) etching the third layer to form the first recessed portion on an upper surface of the third layer (S120); (c) depositing a fourth layer on the upper portion of the third layer etched in (b) (S130); and (d) etching an upper surface of the fourth layer to form the second recessed portion in the fourth layer (S140), wherein the lower layer is the third layer in (b) and the upper layer is the fourth layer in (d).

[0027] The third layer is formed of silicon nitride (Si3N4) and the fourth layer is formed of silicon dioxide (SiO2).

[0028] After step (a) (S110) and before step (b) (S120), the method further includes: (a1) coating the third layer with an electron resist (ER) to form the first recessed portion (S111); and (a2) irradiating a predetermined portion of the electron resist coated in step (a1) with an electron beam (E-Beam) to etch the electron resist into a shape corresponding to the first recessed portion (S112). In step (b), the third layer is etched using the shape of the electron resist obtained in step (a2).

[0029] After step (c) (S130) and before step (d) (S140), the method further includes: (c1) coating the fourth layer with an electron resist (ER) to form the second recessed portion (S131); and (c2) irradiating a predetermined portion of the electron resist coated in step (c1) with an electron beam (E-Beam), thereby etching the electron resist into a shape corresponding to the second recessed portion (S132). In step (d), the fourth layer is etched using the shape of the electron resist obtained in step (c2).

[0030] Meanwhile, a LIDAR having an optical phased array antenna according to the present invention comprises a light source, an optical phased array antenna according to any one of claims 1 to 10, an optical receiving unit that receives light emitted from the optical phased array antenna and then reflected by an object, and a signal processing unit that processes the signal received by the optical receiving unit. Effect of the Invention

[0031] The present invention is expected to be utilized as a core element of vehicle lidar sensors that do not require scanning in the future, and is also expected to be able to fulfill the role of existing CMOS sensors used to obtain 3D images.

[0032] In addition, the present invention provides an effect of reducing perturbation strength and maximizing directivity by forming a grating not only on the upper end of the antenna element waveguide but also on the upper part of the clad layer by etching. [Brief description of the drawings]

[0033] [Figure 1] 1 is a schematic perspective view of an optical phased array antenna according to the present invention; [Diagram 2] FIG. 2 is a cross-sectional view of the optical phased array antenna of FIG. [Diagram 3] FIG. 2 is a conceptual diagram of the optical phased array antenna of FIG. 1. [Figure 4] FIG. 2 is a schematic diagram showing the structure of the optical phased array antenna of FIG. 1. [Diagram 5] 1 is a schematic diagram of a multi-mode interferometer (MMI) constituting an optical distribution section of an optical phased array antenna according to the present invention. [Figure 6] 1 is a graph showing beam directivity in the Z-axis direction of the optical phased array antenna of the present invention and a conventional optical phased array antenna. [Figure 7] 1 is a graph showing the reflected light in the Z-axis direction of the optical phased array antenna of the present invention and the conventional optical phased array antenna. [Figure 8] 1 is a graph showing perturbation strength of the optical phased array antenna of the present invention and a conventional optical phased array antenna; [Figure 9] 1 is a conceptual diagram for an optical phased array antenna with an offset distance of 0. [Figure 10] 1 is a conceptual diagram of an optical phased array antenna according to the present invention; [Figure 11] 1 is a graph of beam directivity for the optical phased array antenna of the present invention according to offset distance. [Figure 12] 1 is a graph showing the upward and downward transmittance of the optical phased array antenna of the present invention according to the offset distance; [Figure 13] 1 is a diagram showing the distribution of optical energy incident along the waveguide of the optical phased array antenna of the present invention. In the original color diagram, yellow and light blue flame-like patterns appear alternately in the left and right direction at the bottom of the diagram, but most of the area is grass green, and there is an orange part in the center of the yellow flame-like pattern. The yellow is about 0.5 to 1 (×10-4), the light blue is about -1 to -0.3 (×10-4), the grass green is about 0 to 0.3 (×10-4), and the orange is about 1 (×10-4). In the black and white diagram, the darkest area is the light blue low level area, and the lightest area is a relatively low level area in the yellow high level area. [Figure 14]This is a diagram showing the distribution of optical energy incident along the waveguide of an optical phased array antenna with an offset distance of 0. In the original color diagram, red flame-like patterns in yellow and blue flame-like patterns in light blue are alternately displayed in the left-right direction at the bottom of the diagram, but most of the area is grass green. In the center of the red flame-like area, an area close to black also appears. The red area is about 1.7 to 2.7 (×10-4), the blackish area is about 3 (×10-4), and the blue area is about -1.3 to -2.7 (×10-4). The yellow, light blue, and green colors are as explained in FIG. 13. In the black and white diagram, the red flame-like area in yellow appears as a black area surrounded by the thinnest linear area. Also, the blue flame-like area in light blue appears as a black area without an enclosed pattern. [Figure 15] This is a diagram showing the distribution of optical energy incident along the waveguide of an optical phased array antenna in which only the upper end lattice exists in the cladding layer. In the original color diagram, red flame-like patterns in yellow and blue flame-like patterns in light blue are alternately displayed in the left-right direction at the bottom of the diagram, but most of the area is grass green. However, the line widths of the yellow and light blue flame-like areas are significantly larger than those in Figure 14. In the black and white diagram, the red flame-like area in the yellow frame appears as a black area surrounded by the thinnest linear area. Also, the blue flame-like area in the light blue frame appears as a black area without a frame pattern. [Figure 16] 13 is a diagram showing the distribution of optical energy incident along the waveguide of an optical phased array antenna in which only the bottom grating exists in the antenna element waveguide. The explanation of the original color figure and the explanation of the area appearing in the black and white figure are the same as in Figs. 14-15. [Figure 17] 1 is a schematic diagram showing a coupler constituting an optical distribution section of an optical phased array antenna according to the present invention; [Figure 18] FIG. 2 is a schematic diagram showing a state in which a metal heater is built into the optical phased array antenna according to the present invention; [Figure 19] 4 is a flow chart of a method for processing an optical output portion of an optical phased array antenna according to the present invention. [Figure 20] 3A to 3C are conceptual diagrams showing steps of a method for processing an optical output portion of an optical phased array antenna according to the present invention. [Figure 21] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Figure 22] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 23] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Figure 24] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 25] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Figure 26] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Figure 27] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Figure 28] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Figure 29] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 30] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 31] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 32] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 33] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. [Diagram 34] 4 is a conceptual diagram of each step of the method for fabricating the optical output portion of the optical phased array antenna according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, an optical phased array antenna of an optical waveguide type having a hybrid lattice structure according to the present invention will be described with reference to the drawings. In this application, 'one direction' is shown as 'X-axis direction' in the drawings, and means the length direction of the optical phased array antenna according to the present invention. Also, 'height direction' is shown as 'Z-axis direction' based on the drawings. However, the directions defined in this application are defined for the convenience of understanding, and do not limit the application of the present invention to the above directions.

[0035] An optical phased array antenna 100 of an optical waveguide type having a hybrid grating structure according to the present invention will be described with reference to FIGS. 1 and 2, and the overall configuration will be referred to in conjunction with FIGS.

[0036] The optical phased array antenna 100 of the optical waveguide type having a hybrid grating structure according to the present invention includes a coupling section 110, an optical distribution section 120, a phase modulation section 130, and an optical output section 200.

[0037] A LIDAR laser transmission module may be configured to include an optical phased array antenna 100 and a light source 50 that supplies a laser beam to an optical distributor 120 of the optical phased array antenna 100. Meanwhile, the LIDAR according to the present invention may further include a laser receiving module that receives the reflected light after the light emitted to the outside from the laser transmission module is reflected by an object.

[0038] The light source 50 is a laser generator that supplies a laser beam to the corresponding optical distributor 120. The laser generator is preferably capable of changing the wavelength of the generated laser, and as an example, the laser generator may be a tunable laser diode. The laser beam output from the optical phased array antenna 100 to the outside can be rotated in one direction according to the change in wavelength of the laser beam supplied to the optical phased array antenna 100. The light generated by the light source 50 is input to the coupling unit 110 of the optical phased array antenna 100.

[0039] Meanwhile, the laser receiving module includes an optical receiving unit that receives light reflected by an object after being emitted from the optical phased array antenna 100, and a signal processing unit that processes the signal received by the optical receiving unit. Here, the optical receiving unit and the signal processing unit are applied to the laser receiving module constituting the conventional LIDAR, and therefore a detailed description thereof will be omitted.

[0040] 3 and 4, the optical distributor 120 divides and transmits the light input to the coupler 110 to a plurality of optical paths, i.e., a plurality of antenna element waveguides. The optical distributor 120 may be composed of a plurality of couplers. As the couplers constituting the optical distributor 120, a multimode interference coupler (MMI), a Y-junction coupler, a directional coupler, or the like may be used. Here, the multimode interference coupler is a multimode interference called MMI, and is shown in FIG. 5.

[0041] The phase modulation unit 130 modulates the phase of the light distributed to each antenna element waveguide by the light distribution unit 120. That is, the phase of the light transmitted through the antenna element waveguide is modulated, and the direction of the laser beam output from the light output unit 200 can be rotated around the X-axis by modulating the phase of the light in the phase modulation unit 130. Although not specifically illustrated in the drawings of the present application, the phase modulation unit 130 can form an electric field by applying a potential using an electrode, and a method of modulating the phase of the light through this can be adopted. However, it is clearly stated that any method of modulating the phase of the light can be applied other than the above method. The structure required for the phase modulation unit 130 is a form in which silicon oxide, silicon nitride, silicon oxide, and silicon are laminated in this order from the top, and the silicon nitride waveguide is surrounded by silicon oxide, and the lattice is formed by etching the silicon nitride waveguide and the silicon oxide layer at the upper end.

[0042] At this time, since the upper silicon nitride has a low refractive index of about 2, it is preferable to set the thickness to 500 nm or more for the purpose of proper mode confinement.

[0043] The optical output unit 200 outputs the laser beam upward while maintaining the phase distribution modulated by the phase modulation unit 130. Referring to Figures 3 and 4, the optical output unit 200 outputs the laser beam in the Z-axis direction from the XY plane, and the output direction of the laser beam output from the optical output unit 200 is steered according to the wavelength of the laser beam input to the optical distribution unit 120 and the phase modulated by the phase modulation unit 130.

[0044] In this regard, referring to FIG. 4, the radiation angle (θ) of the light outputted through the light output unit 200 from the positive direction to the vertical direction can be controlled according to the following Equation 1.

[0045] [Formula 1] JPEG0007631452000001.jpg2856

[0046] As can be seen from Equation 1, the effective refractive index (n eff ), background refractive index (n background ), the operating wavelength (λ), and the pitch (Λ) of the first lead-in portion 223 or the second lead-in portion 231 described below, the radiation angle (θ) can be calculated.

[0047] In the optical output unit 200, an optimized waveguide width must be used to narrow the distance between the antenna element waveguides 220, which is a wide width that reduces the magnitude of the evanescent wave, but the wide width must compensate for the distance between the elements that is closer. In order to directionally radiate the antenna elements upward, a diffraction grating in which the thickness of the silicon nitride layer in the hybrid waveguide is periodically changed is used. In this case, the thickness of the silicon nitride layer is changed so that the phase change experienced in the thin and thick parts satisfies constructive interference at the top and destructive interference at the bottom, so that the radiation is directional upward, and the thicknesses of the upper and lower silicon oxide thin films surrounding the hybrid waveguide are configured to be close to a multiple of half the wavelength to satisfy constructive interference.

[0048] Also, in order to eliminate the symmetry of the vertical refractive index, the maximum thickness of the periodically changed silicon nitride may be thicker than the receiving section and the phase modulation section 130 .

[0049] The shape of the diffraction grating of the antenna element can utilize the width change of the hybrid waveguide, and if the width changes while crossing left and right, the interval between adjacent waveguides can be kept constant, and if the width changes while crossing the surrounding waveguides, the effective refractive index of the mode differs for each waveguide, and therefore the strength of mode coupling is weakened, and the strength of crosstalk of the propagated signal can be reduced. In addition, if a large amount of output is desired in a short distance, the antenna element waveguide 220 can be arranged discontinuously.

[0050] 1 and 2, a detailed structure of the optical phased array antenna 100 according to the present invention will be described. The layers constituting the optical phased array antenna 100 will be described later.

[0051] The optical output section 200 of the optical phased array antenna 100 according to the present invention outputs light modulated by the phase modulation section 130, and includes an antenna element waveguide 220 extending a predetermined length along one direction (X-axis direction) through which the light propagates, and a cladding layer 230 formed to encase the antenna element waveguide 220.

[0052] The antenna element waveguide 220 may be divided into a flat waveguide portion 221 and a lattice antenna portion 222. Here, the flat waveguide portion 221 and the lattice antenna portion 222 are all positioned on an extension line in one direction, and the flat waveguide portion 221 and the lattice antenna portion 222 are sequentially arranged based on one direction.

[0053] The flat waveguide section 221 is formed to have a predetermined length, and the lattice antenna section 222 is formed such that a plurality of first recessed portions 223 are spaced apart from each other along one direction. The flat waveguide section 221 and the lattice antenna section 222 may be formed in the form of a bar made of silicon nitride (Si3N4). The antenna element waveguide 220 of the present invention is disposed on a substrate 224, which is called a wafer, and is buried by being surrounded by a cladding layer 230 made of silicon (SiO2). Here, the upper end surface and the lower end surface of the flat waveguide section 221 and the lattice antenna section 222 may be formed to have the same height, and the height is applied to be 0.56 μm. The flat waveguide section 221 and the lattice antenna section 222 are formed to have a width of 2 μm in the Y-axis direction. Meanwhile, the distance from the upper end face of the flat waveguide section 221 and the lattice antenna section 222 to the upper end face of the cladding layer 230 and the distance from the lower end face to the substrate 224 can be selected as optimal values ​​according to the designer's choice.

[0054] As described above, the lattice antenna unit 222 is formed with a plurality of first recessed portions 223. The first recessed portions 223 are formed to be recessed downward to a predetermined depth from the upper surface of the antenna element waveguide 220. Here, it is preferable that the first recessed portions 223 are recessed to a depth of 0.07 μm from the upper surface of the antenna element waveguide 220. The first recessed portions 223 are formed to have a width corresponding to the width of the antenna element waveguide 220 based on the Y-axis direction.

[0055] The first recessed portion 223 is formed to have a predetermined width from one end to the other end based on the length direction of the antenna element waveguide 220, i.e., one direction, and a plurality of first recessed portions 223 are formed to be spaced apart from each other along the length direction of the antenna element waveguide, i.e., one direction. That is, the first recessed portion 223 and the first protruding portion 225 between the first recessed portions 223 are formed to be alternated along the length direction of the antenna element waveguide. At this time, the first protruding portion 225 and the first recessed portion 223 are formed to be repeated at a predetermined period (a1). Here, the period is 0.85 μm, and the first recessed portion is preferably formed to have a width (b1) of 0.425 μm, which is half of the period, but is not limited thereto, and various values ​​can be applied according to the specifications of the antenna to be manufactured.

[0056] The cladding layer 230 is formed to enclose the antenna element waveguide 220 and is provided on the upper surface of the substrate 224. Here, the cladding layer 230 may support the antenna element waveguide 220 so that it is spaced upward from the substrate 224. Here, the cladding layer 230 is formed such that the height from the lower surface to the lower surface of the antenna element waveguide 220 is greater than the height from the upper surface to the upper surface of the antenna element waveguide 220. That is, the height (h1) from the lower surface of the cladding layer 230 to the lower surface of the antenna element waveguide 220 may be 3.22 μm, and the height (h2) from the upper surface of the cladding layer 230 to the upper surface of the antenna element waveguide 220 may be 1.34 μm, but is not limited thereto and may be variously set according to the type or size of the lidar. In addition, it is preferable that the cladding layer 230 is formed to have a width greater than the width of the antenna element waveguide 220 based on the Y-axis direction.

[0057] Meanwhile, the cladding layer 230 has a second recessed portion 231 recessed downward based on the top surface at a position adjacent to the first recessed portion 223 of the antenna element waveguide 220. Here, it is preferable that the second recessed portion 231 is recessed downward to a depth of 1.3 μm with respect to the top surface of the cladding layer 230 so that the bottom surface is adjacent to the top surface of the antenna element waveguide 220.

[0058] The second recessed portion 231 is formed to have a predetermined width from one end to the other end based on the length direction of the antenna element waveguide 220, and a plurality of them are formed to be spaced apart from each other along the length direction of the antenna element waveguide 220, i.e., along one direction. That is, the second recessed portion 231 and the second protruding portion 232 between the second recessed portions 231 are formed to alternate along the length direction of the antenna element waveguide. Here, the second protruding portion 232 and the second recessed portion 231 are formed to be repeated at a predetermined period (a2). Here, it is preferable that the period is 0.85 μm and the second recessed portion 231 is formed to have a width (b2) of 0.425 μm, which is half of the period, but the present invention is not limited thereto, and various values ​​can be applied according to the specifications of the antenna to be manufactured.

[0059] Also, the cladding layer 230 may have the second lead-in portion 231 at a position spaced apart from the first lead-in portion 223 in the length direction, i.e., in one direction, of the antenna element waveguide 220 so that the second lead-in portion 231 faces a portion of the remaining region of the antenna element waveguide 220 excluding the first lead-in portion 223. That is, the second lead-in portion 231 is formed such that the other end of the second lead-in portion 231 is spaced backward from the other end of the first lead-in portion 223 in the length direction, i.e., in one direction, by a preset offset distance (L). Here, it is preferable that the offset distance is close to 0.3 μm. Also, the second lead-in portion 231 is formed to have a width corresponding to the width of the cladding layer 230 based on the Y-axis direction.

[0060] The second lead-in portions 231 are formed to be spaced apart from each other along the length direction, i.e., one direction, of the antenna element waveguide 220. Here, it is preferable that the second lead-in portions 231 are formed to be spaced apart from each other by a distance corresponding to the length width of the first lead-in portion 223.

[0061] Meanwhile, graphs of beam directivity and reflected light in the Z-axis direction of the optical phased array antenna 100 of the present invention and the conventional optical phased array antenna 100 are shown in Fig. 6 and Fig. 7. In the drawings, a hybrid grating antenna is the optical phased array antenna 100 of the present invention, a wave guide grating antenna is an antenna having a pattern etched on a conventional waveguide, and a cladding grating antenna is an antenna having a pattern etched on a conventional cladding layer 230. Referring to the drawings, in terms of beam directivity, the optical phased array antenna 100 of the present invention shows high efficiency (directionality=95%) compared to an antenna having a pattern etched on a conventional waveguide (directionality=60%) and an antenna having a pattern etched on a cladding layer 230 (directionality=70%). In addition, the optical phased array antenna 100 of the present invention has less reflected light than an antenna having an etched pattern on a waveguide, and is therefore more suitable for FMCW LiDAR.

[0062] 8 shows a graph of perturbation strength for the optical phased array antenna 100 of the present invention and the conventional optical phased array antenna 100. In the drawing, the hybrid grating antenna ('Hybrid Waveguide-Cladding Grating') is the optical phased array antenna 100 of the present invention, the waveguide grating antenna ('Wave Grating Antenna') is an antenna having a pattern etched on a conventional waveguide, and the cladding grating antenna ('Cladding Grating Antenna') is an antenna having a pattern etched on a conventional cladding layer 230. Referring to the drawing, the optical phased array antenna 100 of the present invention is lower than the conventional antenna having a pattern etched on a waveguide, and is therefore suitable for high-resolution lidar applications.

[0063] As described above, the optical phased array antenna 100 according to the present invention can maximize directivity by enhancing the upward transmittance of the antenna and suppressing the downward transmittance through strong interaction between the antenna element waveguide 220 and the lattice structure formed in the cladding layer 230.

[0064] Meanwhile, the strength of the interaction between the two lattice structures can be adjusted by changing the separation distance between the first recessed portion 223 and the second recessed portion 231, that is, the offset distance.

[0065] 9 shows a conceptual diagram of an optical phased array antenna 100 with an offset distance of 0, and FIG. 10 shows a conceptual diagram of an optical phased array antenna 100 according to the present invention. Referring to the drawings, in the case of the optical phased array antenna 100 with an offset distance of 0, the light is directed upward at the front part of the waveguide grating, i.e., one end (circled 1) of the first lead-in part 223, and the light is directed downward at the rear part of the waveguide grating, i.e., the other end (circled 2) of the first lead-in part 223. On the other hand, in the case of the optical phased array antenna 100 according to the present invention, as a result of the interaction between the two gratings, the light is directed downward at the front part of the waveguide grating, i.e., one end (circled 1) of the first lead-in part 223, and the light is directed upward at the rear part of the waveguide grating, i.e., the other end (circled 2) of the first lead-in part 223. Therefore, in the optical phased array antenna 100 of the present invention, the energy of the incident light has a relatively large directivity depending on the magnitude of the offset distance, so that perturbations can be minimized.

[0066] Meanwhile, FIG. 11 shows a graph of the beam directivity of the optical phased array antenna 100 of the present invention depending on the offset distance, and FIG. 12 shows a graph of the upward transmittance and downward transmittance of the optical phased array antenna 100 of the present invention depending on the offset distance.

[0067] Referring to the drawing, it can be seen that as the offset distance increases, the beam directivity, upward transmittance, and downward transmittance of the optical phased array antenna 100 increase, but if the offset distance exceeds 0.3 μm, they decrease. Therefore, it is preferable that the offset distance between the first lead-in portion 223 and the second lead-in portion 231 is equal to or less than 0.3 μm, i.e., close to 0.3 μm.

[0068] Meanwhile, Fig. 13 shows the distribution of optical energy incident along the waveguide of the optical phased array antenna 100 of the present invention, Fig. 14 shows the distribution of optical energy incident along the waveguide of the optical phased array antenna 100 with an offset distance of 0, Fig. 15 shows the distribution of optical energy incident along the waveguide of the optical phased array antenna 100 in which only the second lead-in portion 231, i.e., the upper end lattice, exists in the cladding layer 230, and Fig. 16 shows the distribution of optical energy incident along the waveguide of the optical phased array antenna 100 in which only the first lead-in portion 223, i.e., the lower end lattice, exists in the antenna element waveguide 220. Referring to the drawings, it can be seen that the optical phased array antenna 100 of the present invention has relatively weak perturbation and small beam size compared to other antennas, and is suitable for high-resolution long-distance lidar.

[0069] Meanwhile, the optical output section 200 of the optical phased array antenna 100 of the present invention is configured in such a manner that a lower layer and an upper layer are stacked in the vertical direction on the upper part of a base layer, and a first inlet portion 223 is formed by etching the upper part of the lower layer, and a second inlet portion 231 is formed by etching the upper part of the upper layer.

[0070] 17 is a schematic diagram showing a coupler 121 constituting the optical distributor 120 of the optical phased array antenna 100 according to the present invention. As described above, when the light source 50 is constituted by a laser diode, the mode diameter of the laser beam output from the laser diode is larger than the mode diameter of the waveguide of the optical phased array antenna 100, so the coupling part 110 is designed to have an inverse taper shape (a shape in which the width of the part where the laser beam is input is narrow and the width increases toward the phase modulation part 130) in order to reduce the mode diameter.

[0071] FIG. 5 is a schematic diagram of a multi-mode interference device constituting the optical splitter 120 of the optical phased array antenna 100 according to the present invention. A multi-mode interference device (MMI) is a device used to split light traveling along an antenna element waveguide. Similar to an optical fiber-chip coupler, mode matching between the waveguides is important, and a diamond shape can be used. Here, a mode means a state in which light can travel without energy loss in a waveguide (optical fiber), and the mode shape changes depending on the material and shape of the waveguide and the characteristics of the light. If the mode of light entering a waveguide does not match the mode of the waveguide, the light is quickly attenuated and disappears.

[0072] Referring to FIG. 18, the metal heater 131 of the optical phased array antenna 100 according to the present invention is shown as a schematic diagram of a built-in phase modulation unit 130. The micro-heater, which changes the phase of each light wave by changing the effective refractive index of the antenna element waveguide 220, generates heat as Joule heating due to the resistance of the electrode when current is passed through a metal electrode having a width of a micrometer size, and is configured to enable phase modulation using such a thermo-optical phenomenon. For reference, one of the core elements of the optical phased array antenna 100 is a grating-based Waveguide Grating Antenna (WGA) that emits a beam in the vertical direction of the chip, and an optimized grating structure is developed for the WGA directivity control, and a micro-heater is manufactured to control the divergence angle.

[0073] Meanwhile, FIG. 19 shows a flow chart of a method for fabricating the optical output unit 200 in the optical phased array antenna 100 according to the present invention.

[0074] Referring to the drawing, the method for fabricating the optical output unit 200 of the optical phased array antenna includes steps S110 to S140.

[0075] Step S110 is a step of preparing a silicon-on-insulator (SOI) having first to third layers 11, 12, and 13 stacked thereon, as shown in Fig. 20. Here, it is preferable that the first layer 11 is made of Si, the second layer 12 is made of SiO2, and the third layer is made of Si3N4.

[0076] Meanwhile, after step S110 and before step S120, steps S111 and S112 are further included.

[0077] 21, the step (S111) is a step of coating an electron resist (ER) 21 on the third layer 13 to form the first recessed portion 223. Here, it is preferable that the electron resist 21 is coated so as to entirely cover the upper surface of the third layer 13.

[0078] Step S112 is a step of irradiating an electron beam (E-Beam) to a preset portion of the electron resist 21 coated in step S111 as shown in Fig. 22, and etching the electron resist 21 into a shape corresponding to the first recessed portion 223 as shown in Fig. 23. Particularly, step S120 is configured to etch the third layer 13 using the shape of the electron resist 21 obtained in step S112.

[0079] 24, the third layer 13 is etched to form the first recessed portion 223 on the upper surface of the third layer 13. A portion of the upper side of the third layer 13 exposed to the outside is etched through the etched portion of the electronic resist 21 processed in step S112 to form the first recessed portion 223. When the formation of the first recessed portion 223 is completed, the electronic resist 21 is removed from the third layer 13. Here, the third layer 13 is the lower layer.

[0080] In step S130, as shown in Fig. 25, a fourth layer 14 is deposited on the third layer 13 etched in step S120. Here, the fourth layer 14 is preferably made of silicon dioxide (SiO2). First, the fourth layer 14 is deposited on the third layer 13 to a height of 1.34μm or more, and then the fourth layer 14 is polished to a height of 1.34μm. Through the polishing process, a fourth layer 14 structure with a flat upper surface can be obtained.

[0081] Meanwhile, after step S130 and before step S140, steps S131 and S132 are further included.

[0082] In step S131, an electron resist (ER) 22 is coated on the fourth layer 14 to form a second recessed portion 231 as shown in Fig. 26. Here, it is preferable that the electron resist 22 is coated so as to completely cover the top surface of the fourth layer 14.

[0083] In step S132, an electron beam (E-Beam) is irradiated to a preset portion of the electron resist 22 coated in step S131 as shown in Fig. 27, and the electron resist 22 is etched into a shape corresponding to the second recessed portion 231 as shown in Fig. 28. In particular, in step S140, the fourth layer 14 is etched using the shape of the electron resist 22 obtained in step S132.

[0084] 29, step S140 is a step of etching an upper surface of the fourth layer 14 to form the second recessed portion 231 in the fourth layer 14. An upper portion of the fourth layer 14 exposed to the outside through the etched portion of the electronic resist 22 processed in step S132 is etched to form the second recessed portion 231, and when the formation of the second recessed portion 231 is completed, the corresponding electronic resist 22 is removed from the fourth layer 14. Here, the fourth layer 14 is the upper layer.

[0085] Meanwhile, if the step S140 is completed, a pattern forming step of forming a predetermined circuit pattern on the upper surface of the fourth layer 14 may be further included.

[0086] 30, the pattern forming step coats a photoresist 23 on the upper surface of the fourth layer 14 on which the second recessed portion 231 is formed. At this time, it is preferable to perform a planarization process so that the upper surface of the photoresist 23 is flat.

[0087] Next, as shown in Fig. 31, a mask 31 having light-transmitting portions formed in a shape corresponding to the circuit pattern is set above the photoresist 23, and light is irradiated onto the upper part of the mask 31. Here, only the light that passes through the light-transmitting portions of the mask 31 reaches the photoresist 23, and the photoresist 23 is etched in the portions corresponding to the light-transmitting portions by the light, as shown in Fig. 32. Next, as shown in Fig. 33, a fifth layer 15 is formed on the photoresist 23. At this time, the fifth layer 15 may be made of Au, Cr, etc., which are materials that can generate heat by passing an electric current through them, but it is preferable that the fifth layer 15 is made of Ti, which has a high electrical resistivity.

[0088] When deposition of the fifth layer 15 is completed, the fifth layer 15 exposed on the top of the photoresist 23 is removed, and then the photoresist 23 is removed from the fourth layer 14. At this time, as shown in FIG 34, a portion of the fifth layer 15 that filled the etched portion of the photoresist 23 remains on the fourth layer 14 to form a circuit pattern.

[0089] The description of the embodiments presented is provided to enable any person skilled in the art to use or practice the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments presented herein, but is to be accorded the broadest scope consistent with the principles and novel features presented herein. [Explanation of symbols]

[0090] 100 Optical Phased Array Antenna 110 Joint 120 Light distribution section 130 Phase modulation section 200 Optical output section 220 Antenna element waveguide 221 Flat waveguide section 222 Lattice antenna part 223 First retraction section 224 Base material 230 Cladding layer 231 Second retractable section

Claims

1. 1. An optical phased array antenna, comprising: a coupling portion for receiving a light input from a light source; a light distribution unit that distributes the light propagated from the coupling unit into a plurality of light paths; a phase modulation unit that modulates the phase of the light distributed by the light distribution unit; an optical output section for outputting light modulated by the phase modulation section, the optical output section including an antenna element waveguide through which the light propagates and which is extended by a predetermined length, and a cladding layer formed to encase the antenna element waveguide; The antenna element waveguide is formed with a first recessed portion recessed downward with respect to an upper surface thereof, a second recessed portion is formed in the cladding layer at a position adjacent to the first recessed portion and recessed downward with respect to an upper surface of the cladding layer; The light output unit is configured such that a lower layer and an upper layer are stacked on top of a base layer in a vertical direction, the first recessed portion is recessed from an upper surface of the lower layer, the second recessed portion is recessed from the upper surface of the upper layer; Optical phased array antenna.

2. An optical phased array antenna, comprising: a coupling portion for receiving a light input from a light source; a light distribution unit that distributes the light propagated from the coupling unit into a plurality of light paths; a phase modulation unit that modulates the phase of the light distributed by the light distribution unit; an optical output section for outputting light modulated by the phase modulation section, the optical output section including an antenna element waveguide through which the light propagates and which is extended by a predetermined length, and a cladding layer formed to encase the antenna element waveguide; The antenna element waveguide is formed with a first recessed portion recessed downward with respect to an upper surface thereof, a second recessed portion is formed in the cladding layer at a position adjacent to the first recessed portion and recessed downward with respect to an upper surface of the cladding layer; The second recessed portion of the cladding layer is so that the antenna element can face a part of a remaining region of the antenna element waveguide excluding the first lead-in portion, The antenna element is formed at a position shifted from the first recess along the longitudinal direction of the antenna element waveguide. Optical phased array antenna.

3. An optical phased array antenna, comprising: a coupling portion for receiving a light input from a light source; a light distribution unit that distributes the light propagated from the coupling unit into a plurality of light paths; a phase modulation unit that modulates the phase of the light distributed by the light distribution unit; an optical output section for outputting light modulated by the phase modulation section, the optical output section including an antenna element waveguide through which the light propagates and which is extended by a predetermined length, and a cladding layer formed to encase the antenna element waveguide; The antenna element waveguide is formed with a first recessed portion recessed downward with respect to an upper surface thereof, a second recessed portion is formed in the cladding layer at a position adjacent to the first recessed portion and recessed downward with respect to an upper surface of the cladding layer; The light output unit is configured such that a lower layer and an upper layer are stacked on top of a base layer in a vertical direction, the first recessed portion is formed by etching an upper portion of the lower layer, the second recessed portion is formed by etching an upper portion of the upper layer; Optical phased array antenna.

4. the first recessed portion is formed to have a predetermined width from one end to the other end based on a length direction of the antenna element waveguide, the second lead-in portion is formed to have a predetermined width from one end to the other end based on the length direction of the antenna element waveguide, and the other end is formed to be spaced apart from the other end of the first lead-in portion by a predetermined offset distance along the length direction of the antenna element waveguide. An optical phased array antenna according to any one of claims 1 to 3.

5. The offset distance is 0.3 μm or less.

5. The optical phased array antenna of claim 4.

6. the second lead-in portion is formed to have a width corresponding to a width of the first lead-in portion based on a length direction of the antenna element waveguide, 5. The optical phased array antenna of claim 4.

7. the second recessed portion is recessed downwardly into the upper surface of the clad layer at a predetermined depth so that a bottom surface of the second recessed portion is adjacent to the upper surface of the antenna element waveguide; 5. The optical phased array antenna of claim 4.

8. The first recessed portion is formed so as to be spaced apart from one another along a longitudinal direction of the antenna element waveguide.

2. The optical phased array antenna of claim 1.

9. The second recessed portion is formed in a corresponding clad layer so as to be spaced apart from each other along the length direction of the antenna element waveguide.

9. An optical phased array antenna according to claim 1 or claim 8.

10. The first recessed portions are spaced apart from each other by a length corresponding to a width of the antenna element waveguide in the longitudinal direction.

9. The optical phased array antenna of claim 8.

11. A method for manufacturing an optical phased array antenna according to any one of claims 1 to 3, comprising the steps of: (a) preparing a silicon-on-insulator (SOI) substrate having first, second and third layers stacked thereon (S110); (b) etching the third layer to form the first recessed portion on an upper surface of the third layer (S120); (c) depositing a fourth layer on the third layer etched in step (b) (S130); (d) etching an upper surface of the fourth layer to form the second recessed portion in the fourth layer (S140); the lower layer is the third layer of step (b); the upper layer being the fourth layer of step (d); Manufacturing method.

12. The third layer is silicon nitride (Si ３ N ４ ) is formed, The fourth layer is silicon dioxide (SiO ２ ) was formed, The method of claim 11.

13. After step (a) (S110) and before step (b) (S120), (a1) coating an electron resist (ER) on the third layer to form the first recessed portion (S111); (a2) irradiating an electron beam (E-Beam) onto a predetermined portion of the electron resist coated in (a1), and etching the electron resist into a shape corresponding to the first recessed portion (S112), In the step (b), the third layer is etched using the shape of the electron resist obtained in the step (a2). The method of claim 11.

14. After step (c) (S130) and before step (d) (S140), (c1) coating the fourth layer with an electron resist (ER) to form the second recessed portion (S131); (c2) irradiating an electron beam (E-Beam) onto a predetermined portion of the electron resist coated in (c1), and etching the electron resist into a shape corresponding to the second recessed portion (S132), In the step (d), the fourth layer is etched using the shape of the electron resist obtained in the step (c2). The method of claim 11.

15. A light source; An optical phased array antenna according to any one of claims 1 to 10; an optical receiver for receiving light that is radiated from the optical phased array antenna and then reflected by an object; A signal processing unit that processes the signal received by the optical receiving unit. rider.

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